The present invention relates to recording and/or reproduction of color television signals, and in particular to a circuit for processing the color difference signals so that high quality images are obtained.
While different types of recording medium are currently available for recording color television signals, the usable passband is limited by a variety of factors which include the storage capacity of the recording medium and the performance of the transducer with which the signal is recorded and reproduced. Various attempts have hitherto been made for maximum utilization of the limited passband for recording color television signals which contain a large amount of information such as luminance and chrominance signal components.
The frequency bandwidth of conventional household video tape recorders is currently limited to about 6 MHz which is determined by the head gap and the relative speed of tape thereto. According to one prior art recording format, the color difference components are converted to a lower frequency range of the 6-MHz band and the luminance component is modulated in frequency upon a 3.9 MHz carrier so that the lower sideband of the modulated luminance lies in the range of 1.4 MHz to 3.9 MHz. When transcribing a video tape, the signal reproduced from the tape is amplified prior to being recorded on a second tape to a sufficient level to ensure against noise. However, the reproduced signal needs to be separated by the use of filters for linear amplification of the chroma signal and for nonlinear amplification of the frequency-modulated luminance component to a predetermined saturation level.
One disadvantage of the prior art system is that no separation filters having ideal passband characteristics are currently available, so that the transcribed signal is not exactly the replica of the original signal.